<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		.box1{
			width: 600px;
			height: 200px;
			background: red;
		}
		.box2{
			width: 600px;
			height: 200px;
			background: blue;
		}
		.son{
			width: 180px;
			height: 180px;
			background: green;
			float: left;
			margin:5px;

		}
	</style>
</head>
<body>
	<div class="box1">
		<div class="son">son</div>
		<div class="son">son</div>
		<div class="son">son</div>
	</div>
	<div class="box2"></div>
</body>
</html>